A rare case report: an inextricable shoulder pain as the exclusive presentation of lung adenocarcinoma with metastasis over contralateral clavicle.

Background: Lung cancer is the fourth most common form of the tumor spreading to the bone. Among all patients of lung carcinoma, the most common sites of bone metastasis are vertebrae, ribs, and pelvis. By comparison, the clavicle is an extremely rare site of metastases not only in the population of lung cancers but among all types of tumors. Enlightened by this existing fact, we would like to share our experience of management of an uncommon clavicular metastasis and illuminate the obscure mechanism of its scarcity.

Case Presentation: A 56-year-old female without any preknown systemic disease had suffered from a sole intermittent right shoulder pain without any other discomfort for 3 months. Physical examination performed at our orthopedic department showed tenderness over the right distal third of the clavicle with limited range-of-motion of the right shoulder. EGFR-mutated lung adenocarcinoma with metastasis over the right clavicle resulting in a pathological fracture was diagnosed according to the result of the incisional biopsy. Concurrent chemoradiation therapy accompanied with target therapy was performed. Eighteen months postoperatively, the clavicle pain was found to be subsided with stationary bony lesion under appropriate medication and palliative radiotherapy during the subsequent follow-up.

Conclusions: The clavicle is an exceedingly unusual site with 2% of metastatic involvement of all type of tumors and only 1% among the population of carcinoma of lung due to its scanty red marrow and sparse vascular supply. Despite the unpleasant prognosis of clavicular metastasis from primary lung adenocarcinoma, promising quality of life is achievable under multidisciplinary management.